In nature, animals need to respond rapidly to changes in their environment. This is especially true for males of species in which both males and females help to raise young because males have to both defend territories and care for young. One mechanism that might explain this quick change is the rapid release of testosterone (T). When T is released, animals show a preference for the place in which they were located at the time of T release. We will test whether, in nature, the context (defending a territory at a home range boundary or being a caring parent at a nest) of the T release has an influence on behavior. We predict that when T release occurs near the territory boundary, the animal will interact with intruders, likely in conjunction with ultrasound vocalizations. On the other hand, we predict that when T release occurs near the nest, the animal will focus its attention on its mate and offspring. We will test our predictions by injecting T into monogamous California mouse males at their territory boundary and at their nest and look for behavioral responses using remote sensing methods that include automated radio-telemetry, acoustic recording, and thermal-imaging. Our results are expected to provide evidence that T is an important hormone for regulating relatively rapid tradeoffs among behaviors involving competition and those involving the mate and offspring. This project is an important collaboration between an R1 and small research campus in which all participants will be uniquely trained in innovative approaches that address cutting edge yet fundamental issues in animal behavior. All aspects of this project will reach the broader public through our community outreach program entitled Bats and Mice In Your Backyard and our widely accessed www-based streaming content and field blog. We will broaden participation in this project through recruitment efforts for the field assistant at a local California State University campus near our field site. We also have exercises in place to formally assess our broader impacts.

Project Report

When an individual animal interacts with another individual, it has a physiological response. We are trying to understand how physiological responses can influence current and future behavior. Other studies have shown that hormones, such as testosterone, can increase after a social interaction. An important question is whether this hormone release can influence future behavior. Because some hormones can result in a positive, rewarding feeling, a preference for a location can form in response to the release of a hormone such as testosterone. Thus, any male-male or male-female interaction that results in the release in testosterone may induce an individual to seek out that location repeatedly. Hormone release may therefore influence how individuals use space through the development of preferences for specific locations. We conducted a field study to test whether preference for specific locations based on testosterone release developed in wild California mice (Peromyscus californicus). We used this species because it is strictly monogamous. Both males and females are territorial and take care of the young. This species is one of very few monogamous mammals and is used as a model for studying behaviors associated with monogamy such as pair formation and paternal care. In one year we were able to show that males experiencing short term pulses of testosterone at the nest site (associated with its family) spent more time at the nest site and produced more vocalizations associated with maintenance of the pair bond than males that did not experience short term pulses of testosterone at the nest site. It remains to be explored if these changes translate into increased paternal care. Importantly, these changes occurred despite all of the natural competing demands such as other social interactions, predation risks and other ecological changes that occur naturally in the field. Our research added a new perspective on how testosterone can impact behavior for a variety of species using a novel integration of approaches. Our research had a broader impact in the sciences because of the collaboration between a large midwestern R1 campus and a small southeastern research campus allowing dissemination of research expertise across a wide venue of researchers and students. Undergraduate students and a post-doctoral fellow were uniquely trained in techniques/approaches to address cutting edge issues in animal behavior. We incorporated our field work and the overall study into our established outreach program Bats and Mice In Your Backyard to reach the broader public. Our outreach program consists of a field blog, video from the field, and a dedicated website.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Program Officer
Bruce Cushing
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University of North Carolina Greensboro
United States
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